DESCRIPTION

Getopt::Long::Descriptive is yet another Getopt library. It's built atop Getopt::Long, and gets a lot of its features, but tries to avoid making you think about its huge array of options.

It also provides usage (help) messages, data validation, and a few other useful features.

FUNCTIONS

Getopt::Long::Descriptive only exports one routine by default: describe_options. All GLD's exports are exported by Sub::Exporter.

describe_options

my ($opt, $usage) = describe_options($usage_desc, @opt_spec, \%arg);

This routine inspects @ARGV for options that match the supplied spec. If all the options are valid then it returns the options given and an object for generating usage messages; if not then it dies with an explanation of what was wrong and a usage message.

The $opt object will be a dynamically-generated subclass of Getopt::Long::Descriptive::Opts. In brief, each of the options in @opt_spec becomes an accessor method on the object, using the first-given name, with dashes converted to underscores. For more information, see the documentation for the Opts class.

The $usage object will be a Getopt::Long::Descriptive::Usage object, which provides a text method to get the text of the usage message and die to die with it. For more methods and options, consults the documentation for the Usage class.

$usage_desc

The $usage_desc parameter to describe_options is a sprintf-like string that is used in generating the first line of the usage message. It's a one-line summary of how the command is to be invoked. A typical usage description might be:

$usage_desc = "%c %o <source> <desc>";

%c will be replaced with what Getopt::Long::Descriptive thinks is the program name (it's computed from $0, see "prog_name").

%o will be replaced with a list of the short options, as well as the text "[long options...]" if any have been defined.

The rest of the usage description can be used to summarize what arguments are expected to follow the program's options, and is entirely free-form.

Literal % characters will need to be written as %%, just like with sprintf.

@opt_spec

The @opt_spec part of the args to describe_options is used to configure option parsing and to produce the usage message. Each entry in the list is an arrayref describing one option, like this:

The first value in the arrayref is a Getopt::Long-style option specification. In brief, they work like this: each one is a pipe-delimited list of names, optionally followed by a type declaration. Type declarations are '=x' or ':x', where = means a value is required and : means it is optional. x may be 's' to indicate a string is required, 'i' for an integer, or 'f' for a number with a fractional part. The type spec may end in @ to indicate that the option may appear multiple times.

For more information on how these work, see the Getopt::Long documentation.

The first name given should be the canonical name, as it will be used as the accessor method on the $opt object. Dashes in the name will be converted to underscores, and all letters will be lowercased. For this reason, all options should generally have a long-form name.

The second value in the arrayref is a description of the option, for use in the usage message.

Special Option Specifications

If the option specification (arrayref) is empty, it will have no effect other than causing a blank line to appear in the usage message.

If the option specification contains only one element, it will be printed in the usage message with no other effect.

If the option specification contains a third element, it adds extra constraints or modifiers to the interpretation and validation of the value. These are the keys that may be present in that hashref, and how they behave:

If option A has an "implies" entry, then if A is given, other options will be enabled. The value may be a single option to set, an arrayref of options to set, or a hashref of options to set to specific values.

required

required => 1

If an option is required, failure to provide the option will result in describe_options printing the usage message and exiting.

hidden

hidden => 1

This option will not show up in the usage text.

You can achieve the same behavior by using the string "hidden" for the option's description.

one_of

one_of => \@subopt_specs

This is useful for a group of options that are related. Each option spec is added to the list for normal parsing and validation.

Your option name will end up with a value of the name of the option that was chosen. For example, given the following spec:

(Internally, all constraints are translated into Params::Validate options or callbacks.)

%arg

The %arg to describe_options is optional. If the last parameter is a hashref, it contains extra arguments to modify the way describe_options works. Valid arguments are:

getopt_conf - an arrayref of strings, passed to Getopt::Long::Configure
show_defaults - a boolean which controls whether an option's default
value (if applicable) is shown as part of the usage message
(for backward compatibility this defaults to false)

prog_name

This routine, exported on demand, returns the basename of $0, grabbed at compile-time. You can override this guess by calling prog_name($string) yourself.

OTHER EXPORTS

-types

Any of the Params::Validate type constants (SCALAR, etc.) can be imported as well. You can get all of them at once by importing -types.

-all

This import group will import -type, describe_options, and prog_name.

CUSTOMIZING

Getopt::Long::Descriptive uses Sub::Exporter to build and export the describe_options routine. By writing a new class that extends Getopt::Long::Descriptive, the behavior of the constructed describe_options routine can be changed.

The following methods can be overridden:

usage_class

my $class = Getopt::Long::Descriptive->usage_class;

This returns the class to be used for constructing a Usage object, and defaults to Getopt::Long::Descriptive::Usage.